[Comparison and application of direct and indirect methods in establishing reference intervals for coagulation tests]

This study aimed to establish adult reference intervals for coagulation parameters using the CN-6000 fully automated coagulation analyzer. It also compared the applicability of direct and indirect methods in different populations. A cross-sectional and retrospective design was employed. The direct method included patients from the colorectal surgery and dermatology departments, as well as healthy participants from phase I clinical trials, admitted to the West Campus of China-Japan Friendship Hospital from April to December 2023. Participants were divided into two age groups: younger adults (18-64 years) and older adults (≥65 years). Coagulation parameters were tested, and reference intervals were determined. The indirect method applied the refineR algorithm to analyze coagulation data from non-ICU patients during the same period. The performance of both methods was evaluated in healthy participants, relatively healthy patients, and patients with high disease prevalence. The results showed that the direct method yielded similar reference intervals for APTT, PT, and TT in younger and older groups, with combined intervals of 23.7-31.2 seconds, 10.4-12.8 seconds, and 14.7-17.5 seconds, respectively. However, the Fib showed a significant difference between the two groups (U=1 052 023, P<0.01), and separate reference intervals were established: 1.7-4.5 g/L for the younger group and 2.1-4.6 g/L for the older group. The reference intervals derived by the indirect method are similar to those from the direct method: APTT 23.8-31.4 seconds, PT 10.4-13.0 seconds, TT 14.5-17.4 seconds, and Fib 1.8-4.3 g/L (18-64 years) and 2.1-4.5 g/L (≥65 years). In relatively healthy patients, the reference intervals obtained by both methods were comparable, but significant differences were observed in patients with high disease prevalence. In conclusion, this study established localized reference intervals for the CN-6000 fully automated coagulation analyzer. The indirect method can serve as an alternative to the direct method in healthy and relatively healthy populations. However, its applicability in populations with high disease prevalence is limited and requires cautious interpretation in the context of clinical settings.